1. Field of the Invention
The present invention relates generally to wireless terminals and more particularly to the mobility of addressing in wireless networks.
2. Description of Related Art
Wireless Broadband Access (“WBA”) based systems have been designed to have operational characteristics that are indistinguishable from Cable or DSL methods of broadband access from the viewpoint of the customer. However, wireless systems are subject to network termination specific substantial signal fading and have the ability to connect using multiple network termination points. In many systems, customer premises equipment (“CPE”), including personal computers (“PCs”), may experience multiple disconnects and reconnects among various different base stations.
Wireless systems may be viewed as multiple logical modems connected through different Network Termination points via different virtual cables, where the system is able to pick the best signal strength at the time that it is connected to an end-point. As time passes, fading on the virtual cable causes the logical modem to disconnect from its current base station and the subscriber station directs the modem to reconnect based on best available signal strength. This behavior can be repeated many times. Fading may be apparently random or based on predictable patterns.
CPE response to fading and disconnect is generally dependent on the type of base station to which it connects. For a Routed base station, the IP address of the CPE changes to enable routing of packets to the CPE through the new subnet. The easiest method to force a CPE to seek a new IP address is to power cycle the CPE facing network interface whenever the subscriber station connects to a different base station. However, the change of IP address is disruptive causing shutdown all network connections in use by application in the CPE. Active connections, whether IP streaming or download in progress, have to be terminated and re-started using the newly-obtained IP address. Also, in many business uses, connections are made from the Internet to the CPE as well from the CPE to the Internet. For these connections, the CPE IP address must be advertised when changed. Even when Dynamic DNS method is being used the DNS update is a slow process and takes hours and sometimes days to spread out in the Internet.
For bridged base stations, the connection between original and new base stations is important. If the base stations are not in the same layer-2 network then the problems described for the routed BS will be observed. If the two base stations are within the same layer-2 network, the CPE does not have to change its IP address and will only experience a brief period of packet drop of seconds. However, a new set of network topology problems will be observed. For example, any broadcast packet will be repeated over all connected base stations, potentially causing a broadcast storm. Malicious users could use broadcast storms to run theft of service and denial of service attacks. Furthermore, identification and debugging of network problems is made difficult. The use of Dynamic VLANs may solve broadcast storm issues and may provide some IP address mobility. However, the initial IP address and VLAN assignment process can cause random distribution of IP addresses, resulting in an expanded and sometimes uncontrollable broadcast domain.